As the development of nearshore wind energy resources reaches saturation

the exploitation and utilization of offshore wind energy are garnering increasing attention. voltage source converter-based high voltage direct current (VSC-HVDC) technology

with its flexible controllability

capacity for islanded operation

and advantages in long-distance power transmission

has emerged as the preferred choice for offshore wind power transmission. However

the large-scale integration of offshore wind VSC-HVDC projects poses stability challenges to the power grid

including issues such as weak systems

low inertia

and inadequate voltage support. Consequently

enhancing the support capabilities of offshore wind VSC-HVDC transmission systems has become a significant research focus internationally. This paper initially introduces the typical topology and fundamental control strategies of offshore wind VSC-HVDC transmission systems. It then examines

from the perspectives of active and reactive power support

the methods and limitations of achieving active support through additional control under the grid-following control structure. Subsequently

it explores the requirements and standards for grid-forming control technologies and analyzes various technical routes along with their characteristics. Lastly

it outlines the development trends and identifies the key issues and challenges currently encountered in research and engineering applications.